Citizens Advice received an average of six complaints each day about gyms and fitness clubs during 2017, the charity has revealed.
It is advising consumers to think carefully before signing up for membership in 2018.
In the year to the end of November it said it helped sort out 3,500 problems involving gyms and fitness studios.
Over the same period, 60,000 people looked at its web pages for advice on how to cancel membership.
However, the number of unhappy customers in 2017 was in line with previous years.
Among the typical complaints were:
- gyms being closed for long periods of time
- classes being shorter than advertised
- poor quality facilities
- people being held in a contract unfairly
"At this time of year we're bombarded with offers for health and fitness memberships, which can ask for a lot of money or commitment up front," said Kate Hobson, consumer expert at Citizens Advice.
"It's really important to do your homework before you sign up to any gym, health club or fitness studio. Make sure you know how long you're committing for, how much it will cost you, and think about how often you'll need to use it for it to make sense on your budget."
Previous research by Citizens Advice has found that many people get trapped paying gym subscriptions which they never use.